Chitin is a natural polysaccharide of major importance. This biopolymer is synthesized by an enormous number of living organisms; considering the amount of chitin produced annually in the world, it is the most abundant polymer after cellulose. The most important derivative of chitin is chitosan, obtained by partial deacetylation of chitin under alkaline conditions or by enzymatic hydrolysis. Chitin and chitosan are known to have important functional activities but poor solubility makes them difficult to use in food and biomedicinal applications. Chitooligosaccharides (COS) are the degraded products of chitosan or chitin prepared by enzymatic or chemical hydrolysis of chitosan. The greater solubility and low viscosity of COS have attracted the interest of many researchers to utilize COS and their derivatives for various biomedical applications. In light of the recent interest in the biomedical applications of chitin, chitosan, and their derivatives, this review focuses on the preparation and biological activities of chitin, chitosan, COS, and their derivatives.

Numerous plants have been documented to contain phenolic compounds. Thymol is one among these phenolic compounds that possess a repertoire of pharmacological activities, including anti-inflammatory, anticancer, antioxidant, antibacterial, and antimicrobial effects. Despite of the plethora of affects elicited by thymol, its activity profile on gastric cancer cells is not explored. In this study, we discovered that thymol exerts anticancer effects by suppressing cell growth, inducing apoptosis, producing intracellular reactive oxygen species, depolarizing mitochondrial membrane potential, and activating the proapoptotic mitochondrial proteins Bax, cysteine aspartases (caspases), and poly ADP ribose polymerase in human gastric AGS cells. The outcomes of this study displayed that thymol, via an intrinsic mitochondrial pathway, was responsible for inducing apoptosis in gastric AGS cells. Hence, thymol might serve as a tentative agent in the future to treat cancer.

Recent reports have shown the antidiabetic effect of Moringa oleifera from various parts of the world. However, M. oleifera from Cambodia has never determined. Therefore, the aim of this study was to assess the antidiabetic effect of M. oleifera extract from Cambodia. The leaf ethanolic extract contained flavonoids (31.90 mg/mL), polyphenols (53.03 mg/mL), lycopene (0.042 mg/mL), and ß-carotene (0.170 mg/mL), and possessed 2,2-diphenyl-1-picrylhydrazyl, hydrogen peroxide, and hydroxyl radical scavenging activities of 92.40, 99.25, and 83.57 TE/μM at 1 mg/mL, respectively. Db/db mice were orally administered the leaf extract (150 mg/kg/day) for 5 weeks. M. oleifera treatment significantly ameliorated the altered fasting plasma glucose (from 483 to 312 mg/dL), triglyceride (from 42.12 to 23.00 mg/dL), and low-density lipoprotein cholesterol (from 107.21 to 64.25 mg/dL) compared to control group, and increased the insulin levels from 946 ± 92 to 1678 ± 268 pg/mL. The histopathological damage and expression levels of tumor necrosis factor-alpha, interleukin (IL)-1β, IL-6, cyclooxygenase-2, and inducible nitric oxide synthase in renal tissue decreased. These results indicate the potential antidiabetic benefits of M. oleifera ethanolic leaf extract.

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Chitosan, which is derived from chitin, has drawn much attention due to its low toxicity and potential use in medical and pharmaceutical applications. The biological activities of chitosan have been shown to depend on its molecular weight (MW) and degree of deacetylation. In this study, we investigated whether oral chitooligosaccharides, which are easily absorbed into the body, can reduce the plasma level of lipid in smokers and non-smokers because smoking is a high-risk factor for cardiovascular diseases. All healthy men (11 smokers and 8 non-smokers) consumed 500 mg of chitooligosaccharides in water twice daily before a meal (breakfast and dinner) over a 6-week period. Total cholesterol and low-density lipoprotein cholesterol levels were significantly decreased in both the smoker group and non-smoker group when compared with baseline. These results suggest that low MW chitooligosaccharides would be an effective dietary supplement for lowering cholesterol level.